D A T A S H E E T
COMMAND DEFINITIONS
Writing specific address and data commands or sequences
into the command register initiates device operations.
Table 5 on page 18 defines the valid register command se-
quences. Writing incorrect address and data values or
writing them in the improper sequence resets the device to
reading array data.
If DQ5 goes high during a program or erase operation, writ-
ing the reset command returns the device to reading array
data (also applies during Erase Suspend).
Autoselect Command Sequence
The autoselect command sequence allows the host system
to access the manufacturer and devices codes, and deter-
mine whether or not a sector is protected. Table 5 on
page 18 shows the address and data requirements. This
method is an alternative to that shown in Table 4 on page 12,
which is intended for PROM programmers and requires VID
on address bit A9.
All addresses are latched on the falling edge of WE# or CE#,
whichever happens later. All data is latched on the rising
edge of WE# or CE#, whichever happens first. Refer to the
appropriate timing diagrams in the AC Characteristics sec-
tion.
Reading Array Data
The autoselect command sequence is initiated by writing two
unlock cycles, followed by the autoselect command. The de-
vice then enters the autoselect mode, and the system may
read at any address any number of times, without initiating
another command sequence. A read cycle at address
XX00h retrieves the manufacturer code. A read cycle at ad-
dress 01h in word mode (or 02h in byte mode) returns the
device code. A read cycle containing a sector address (SA)
and the address 02h in word mode (or 04h in byte mode) re-
turns 01h if that sector is protected, or 00h if it is unpro-
tected. Refer to Table 2 on page 11 and Table 3 on page 11
for valid sector addresses.
The device is automatically set to reading array data after
device power-up. No commands are required to retrieve
data. The device is also ready to read array data after com-
pleting an Embedded Program or Embedded Erase algo-
rithm.
After the device accepts an Erase Suspend command, the
device enters the Erase Suspend mode. The system can
read array data using the standard read timings, except that
if it reads at an address within erase-suspended sectors, the
device outputs status data. After completing a programming
operation in the Erase Suspend mode, the system may once
again read array data with the same exception. See “Erase
Suspend/Erase Resume Commands” for more information
on this mode.
The system must write the reset command to exit the au-
toselect mode and return to reading array data.
Word/Byte Program Command Sequence
The system must issue the reset command to re-enable the
device for reading array data if DQ5 goes high, or while in
the autoselect mode. See the Reset Command‚ on page 15
section, next.
The system may program the device by word or byte, de-
pending on the state of the BYTE# pin. Programming is a
four-bus-cycle operation. The program command sequence
is initiated by writing two unlock write cycles, followed by the
program set-up command. The program address and data
are written next, which in turn initiate the Embedded Pro-
gram algorithm. The system is not required to provide further
controls or timings. The device automatically generates the
program pulses and verifies the programmed cell margin.
Table 5 on page 18 shows the address and data require-
ments for the byte program command sequence.
See also Requirements for Reading Array Data‚ on page 9
for more information. The Read Operations table provides
the read parameters, and Figure 14‚ on page 28 shows the
timing diagram.
Reset Command
Writing the reset command to the device resets the device to
reading array data. Address bits are don’t care for this com-
mand.
When the Embedded Program algorithm is complete, the de-
vice then returns to reading array data and addresses are no
longer latched. The system can determine the status of the
program operation by using DQ7, DQ6, or RY/BY#. See
Write Operation Status‚ on page 19 for information on these
status bits.
The reset command may be written between the sequence
cycles in an erase command sequence before erasing be-
gins. This resets the device to reading array data. Once era-
sure begins, however, the device ignores reset commands
until the operation is complete.
Any commands written to the device during the Embedded
Program Algorithm are ignored. Note that a hardware reset
immediately terminates the programming operation. The
Byte Program command sequence should be reinitiated
once the device has reset to reading array data, to ensure
data integrity.
The reset command may be written between the sequence
cycles in a program command sequence before program-
ming begins. This resets the device to reading array data
(also applies to programming in Erase Suspend mode).
Once programming begins, however, the device ignores
reset commands until the operation is complete.
Programming is allowed in any sequence and across sector
boundaries. A bit cannot be programmed from a 0 back
to a 1. Attempting to do so may halt the operation and set
DQ5 to 1, or cause the Data# Polling algorithm to indicate
the operation was successful. However, a succeeding read
will show that the data is still 0. Only erase operations can
convert a 0 to a 1.
The reset command may be written between the sequence
cycles in an autoselect command sequence. Once in the au-
toselect mode, the reset command must be written to return
to reading array data (also applies to autoselect during
Erase Suspend).
January 23, 2007 Am29SL400C_00_A6
Am29SL400C
15
AMD [ AMD ]
